“A DTG t-shirt file needs a minimum of 300 DPI at a 4500 × 5400 px canvas”

4500 × 5400 px at 300 DPI is consistent (15 × 18 in), and Printify's page presents it as its recommended master spec, but it is not a stated minimum. The same page says 300 DPI is not strictly needed for a small print, and Printful's DTG guide (the only non-claimant source) says most products need at least 150 DPI, with 300 DPI only for items like phone cases and stickers. No source gives 4500 × 5400 px as a DTG minimum.